Impact Of Reverberation Research Articles

ДОСЛІДЖЕННЯ АКУСТИЧНОГО СЕРЕДОВИЩА СУЧАСНИХ БАГАТОФУНКЦІЙНИХ КОМПЛЕКСІВ

This article examines the issue of acoustic comfort and noise pollution within multifunctional residential complexes in Lviv, where public facilities are situated in the ground-level space. The relevance of such a study is confirmed by numerous scientific conclusions that excessive noise exposure negatively affects human health, while this problem remains poorly understood and ignored in Ukraine. According to the research method, 5 multifunctional complexes were selected in different parts of Lviv. Within these complexes, 5–6 points were installed, and measurements were made using the RFT 00 014 pulse sound level meter on different days and at different times of the day. The choice of points was primarily based on the geometric shapes of the buildings (shape breaks, confined spaces, etc.) According to the results of the field measurements, it was found that most multifunctional complexes comply with the state standards for acoustic comfort, but some buildings were exposed to excessive noise load. Hence, a multitude of regularities and correlations were established between the excessive sound level meter values and the characteristics of these complexes. For example, buildings with a closed, perimeter form of construction provide noise reduction of up to 15–20 dB, but its effectiveness can be reduced due to large through passages and traffic directly next to the building. Moreover, the impact of reverberation within such covered courtyards remains unclear, as a cursory analysis shows that playground activity causes an increase in noise of 5 to 15 dB, but the sample size of this study is not sufficient to draw objective conclusions. In addition, the road surface material is an important factor, especially in the context of historic city centres where it is made of basalt paving stones. Traffic on such roads generates a much higher noise level than traffic on asphalt. Following these results, several possible solutions to the noise load problem were analysed, and the importance of conducting similar studies in the future was proven.

Direction of arrival estimation in reverberant environments using a single vibration sensor on an elastic panel

The vibrational response of an elastic panel to an incoming acoustic pressure wave is dependent on the coupling between the incident angle and the panel’s bending modes. By examining the relative modal excitations recorded by a single structural vibration sensor affixed to the panel, the direction of arrival (DOA) of the incident wave may be inferred. In reverberant environments, determination of the DOA of a sound source is complicated by acoustic reflections. Panel microphones may be particularly susceptible to this effect due to their large surface areas and finite modal decay times. A study on the impact of reverberation on DOA estimation using panel microphones was conducted. The panel’s response to wake word utterances was recorded in eight spaces, with reverberation times (RT60s) ranging from 0.27 to 3.00 s. These responses were used to train neural networks for DOA estimation. Results indicate an inverse relationship between RT60 and DOA estimation reliability. Within ±5°, DOA estimation reliability was measured at 95% in the least reverberant space and decreased to 78% in the most reverberant space. Results also suggest that DOA estimation using panel microphones can adapt to diverse acoustic environments by training the system with data from multiple spaces with different RT60s.

The impact of reverberation on speech intelligibility in cochlear implant recipients

Listening to speech in an environment with reverberation can be challenging for both the normal and impaired auditory system. However, it has been shown for both normal- and impaired-hearing listeners that it is the late reflections that are responsible for degrading intelligibility, whereas early reflections actually aid intelligibility by increasing the effective signal-to-noise ratio. Contrastingly, studies conducted with cochlear implant (CI) recipients have suggested that CI recipients have almost no tolerance for reverberation and that they are negatively impacted by both early and late reflections. The main objective of the current study is to re-evaluate the influence of reverberation on speech intelligibility in CI recipients using more authentic virtual auditory environments. Unlike previous studies in this area, this study was conducted using a loudspeaker-based auralization system rather than non-individualized binaural room simulations. Speech intelligibility was measured in simulations of a range of actual physical rooms with plausible source-receiver distances, both with and without late reflections. The results show that the effect of reverberation is much smaller than previously suggested, especially with short source-receiver distances. Furthermore, the results suggest that, in contrast to previous literature, early reflections may not actually be detrimental to CI recipients.

Congruent and Incongruent Semantic Context Influence Vowel Recognition

The influence of sentence context on the recognition of naturally spoken vowels degraded by reverberation and Gaussian noise was investigated. Target words were paired to have similar consonant sounds but different vowels (e.g., map/mop) and were embedded early in sentences which provided three types of semantic context. Fifty-eight normal-hearing, young adults were presented with sentences in which acoustic and semantic cues agreed either weakly (neutral) or strongly (congruent) or the cues strongly disagreed (incongruent). One vowel pair (/epsilon/-/ae/) was selected to be easier to recognize than the other (/a/-/ae/). Changes induced in the spectra of the vowels by degradation showed that the impact of reverberation combined with noise was quite different from either condition alone. The recognition performance of participants (n=26) for isolated word stimuli matched the predictions of the frequency analysis. In sentences the recognition of the vowel was strongly influenced by the subsequent context; performance was best with congruent context and worst with incongruent context. The deleterious impact of incongruent context was larger than the helpful impact of congruent context. Incongruent context effects were greatest in noise but were also found in quiet and in reverberation.

Affective speaker state analysis in the presence of reverberation

Little is known about the impact of reverberation on performance of running speaker state classification systems. This study thus aims to approach the topic by measuring effects on a state-of-the-art engine with consideration of six public room impulse responses for convolution of the affective speech signals of three standard datasets comprising of emotion and interest. Speech data thereby is given by this year’s INTERSPEECH Paralinguistic Challenge corpus TUM AVIC and the frequently used Berlin and eNTERFACE sets. The room impulse responses comprise rooms in private apartments, chapels, a factory hall, and a van. Speaker independent performance after speaker adaptation is investigated. To cope with reverberation, matched condition learning and acoustic space adaptation are considered as efficient means. By that a report is provided on suitability of feature types given the type of impulse response. In the result almost all occurring corruption arising from reverberation can be restored, yet the general impact varies with the type of room or acoustic environment.

Impact of reverberation in flared accretion discs on temporal characteristics of X-ray binaries

Observations suggest that accretion discs in many X-ray binaries are likely flared. An outer edge of the disc intercepts radiation from the central X-ray source. Part of that radiation is absorbed and re-emitted in the optical/UV spectral ranges. However, a large fraction of that radiation is reflected and appears in the broad-band X-ray spectrum as a Compton reflection bump. This radiation is delayed and variability is somewhat smeared compared with the intrinsic X-ray radiation. We compute response functions for flat and flared accretion discs and for isotropic and anisotropic X-ray sources. A simple approximation for the response function which is valid in the broad range of the disc shapes and inclinations, inner and outer radii, and the plasma bulk velocity is proposed. We also study the impact of the X-ray reprocessing on temporal characteristics of X-ray binaries such as the power spectral density, auto- and cross-correlation functions, and time/phase lags. We propose a reprocessing model which explains the secondary peaks in the phase lag Fourier spectra observed in Cyg X-1 and other Galactic black hole sources. The position of the peaks could be used to determine the size of the accretion disc.